Blade retaining means



May 3, 1960 c. E. HocKERT ETAL 2,935,296

BLADE RETAINING MEANS Filed Dec. 2e, 1951 v fw -v L INVENTORS.

87 MMSLM,

R/VEKSZ BLADE RETAJNING MEANS Chester E. Hockert and Leslie R. Smith,Indianapolis, ind., assigner-s to General Motors Corparation, a cor'-poration of Delaware Application December 26, 1951, Serial No. 263,436

6 Claims. (Cl. 253-77) This invention relates to blading of a typesuitable for use in elastic tiuid machines such as axial tiowcompressors and turbines and the like and has for its purpose theprovision of a simple and inexpensive blade retaining means whichefliciently secures a footed blade against movement in a blade carryingmember and which greatly facilitates removal of a damaged blade withoutdamage to the blade carrying member.

ln one form of blade retaining means which has been proposed heretofore,a footed blade is secured against movement in a slot contained in ablade carrying member by a retaining pin extending between the bladecarrying member and the foot of the blade. The pin is constructed fromsoft material so as to be sheared off when the blade is driven from theslot for removal. This results in freezing of the pin in the bladecarrying member and may necessitate drilling to effect removal of thepin which oftentimes results in damage to the blade carrying member.

ln accordance with the present invention, the retaining pin is formedfrom material having a high shear strength, preferably greater than thefoot of the blade and the location of the pin with respect to the end ofthe blade foot in such that, when removal of a damaged blade becomesnecessary, a portion of the foot of the blade may be broken otf readilywithout shearing or damaging the pin, thereby releasing the blade footfrom the pin and facilitating removal of both the blade and pin withoutdamage to the blade carrying member.

The principal objects of the invention are to provide an improvedstructure for bladed machines such as compressors and to facilitate theremoval of damaged blades therefrom.

The preferred manner in which these objects of the invention arerealized together with the features and advantages attending theinvention, will appear more fully from the following detaileddescription and drawings, wherein; Figure l is a fragmentarylongitudinal sectional view of an axial flow compressor employing bladeretaining means in accordance with the invention; Figure 2 is afragmentary detail sectional View of a retaining means in accordancewith the invention in the same plane as Fig. l; Figure 3 is afragmentary transverse sectional view taken in the plane 3 3 of Figure2; and Figure 4 is a View illustrating removal of a blade in accordancewith the invention.

Referring to the drawings, the invention is shown embodied in the rotorof an axial-flow compressor of a type employed in gas turbine aircraftjet engines. Only a portion of the compressor is shown, the remainder ofthe engine being omitted in the interest of clarity of the drawings andconciseness of the specification, since the general structure of such anengine is well understood by those skilled in the art.

The compressor shown in Figure l is of the multi stage type andcomprises a casing or stator 1t) which mounts a number of rows of statorvanes i2 and a rotor member mounted on a shaft (not shown) and definedICC by a plurality of axially spaced rotor disks 14 each having a numberof rotor blades 16 mounted about the circumference thereof.

The compressor casing is formed by a pair of semicylindrical sectionswhich are fastened together by means of anges (not shown) provided alongthe sides thereof. The stator vanes 12 of each stator stage are mountedbetween outer and inner shroud bands 18 and 2b, both of which areconstituted by a pair of semi-circular segments corresponding to thehalves of the casing 10. The outer shroud band 18 is seated in a groove22 in the inner surface of the casing, and retained in a suitable manner(not shown). The inner shroud band 20 comprises a pair of concentricchannel members 24, 26 having superimposed webs, which may be spotwelded together, and inwardly directed tlanges. The outer shroud band 18and the inner shroud band 2t) function principally to support andradially space the stator vanes 12, the inner shroud band servingfurther to provide an elfective fluid seal between the stationary andmoving parts of the compressor. The ends of the stator vanes are shapedto provide projecting tangs or tenons 28 which are received in aperturesin the shroud bands. The tenions are headed, welded, or brazed to securethe vanes 12 to the shroud bands.

The rotor disks 14, which are mounted for rotation in known manner on astub shaft (not shown) journaled within the compressor casing are eachconstituted by a thickened rim 30 and a spacing ring or flange 32integrally formed thereon and extending rearwardly therefrom. The afterend 34 of the spacing ring of each rotor disk engages a mating shoulder36 formed in the forward edge of the rim of the succeeding rotor disk.The rotor disks are coupled by a number of short dowel pins 3S whichextend parallel to the axis of the compressor and are closely fitted inholes 40 circumferentially spaced about the edge of the spacing ring. Anumber of similar openings 42 are provided in the forward edge of eachrotor wheel rim to receive the pins 38 extending from the spacing ring.The pins 38 serve to lock the rotor wheels against rotational movementrelative to one another and to transmit torque therebetween. The disksare held assembled by a tie bolt (not shown) extending between the hubsof the end disks of the assembly in known manner.

As best shown in Figure 3, the rotor blades 16 are provided with anintegrally formed foot 44 which is received in one of a plurality ofmating dovetail slots 46 formed in and spaced about the periphery of therim 30 of each rotor wheel. For the purpose of securing the bladeagainst movement in the dovetail slot, a transverse slot 4S (Figs. 2 and3) is formed intermediate the ends of the foot of the blade to receive aretaining pin 50 which is driven through a hole 52 in the after portionof the wheel rim after a blade is located in its slot, whereby a simple,etiicient, positive lock is provided between the blade and the rotorrim. The pin is retained by friction in the hole 52.

The foot recess 48 may extend transversely across the base of the footof the blade and is preferably located a short distance from thedownstream end of the blade foot.

The rim of the rotor disk and the pin 50 are preferably of a strongmaterial such as alloy steel. The blade foot may be of a more easilyfractured or broken material. in any event, the size of the pin 50 andthe thickness of the lip 54 on the blade foot behind the slot 48 may beso proportioned that if the blade is driven forward in the slot, the lip54 will be broken off without bending or damaging the pin.

The removal of the blade by breaking the frangible lip 54 is illustratedin Fig. 4. After the blade is driven out, the pin Si) may be driven orpressed out preparatory to inserting a new blade. While the removaloperation damages the blade, this is immaterial, as the blades are Y 3not ordinarily removed unless they have been damaged. The removal of theundamaged pin does not damage the rotor.

Where the Vblade 'root groove has a substantial radial component due tothe taper of the rotor surface, as particularly appears in theleft-handV disk of Fig. 1,V centrifugal force urges the bladerearwardly; This force is exerted against the'pin 50 by the main-body ofthe root, which is easily capable of taking this load.

Even ifthe forces on the blade tend Vto slide it so as 'to load the lip54, the latter can be made strong enough to accept the operating load,but to break when the blade root isY driven out for replacement.

There is thusrprovidedra simple and inexpensible blade retaining Ymeanswhich is not only simple to install and replace, but which also providesan efficient positive lock for securing a footed blade in a bladecarrying member and` which greatly facilities removal of a damaged bladefrom itsslot without dmage to the blade carrying member. f Y

Although the present invention has been described with reference to onespecific embodiment, it'will be understood that the invention issusceptible of embodiment in other forms. f

We claim: Y

l, In combination, a blade having a foot having axially extending sidesand transversely extending ends, a blade carrying member containing amating axially extending slot for slidably receiving said blade foot,the blade foot having a recess formed therein adjacent one end thereof,and means for retaining said blade in said slot comprising a pininserted from said blade carrying member to engage Y within the recessVin said blade foot, the pin being more resistant to fracture than theportion of the blade foot between said recess and said one end, wherebythe said portion of said blade foot may be readily broken oi to freesaid blade of said pin for removal of the blade.

2. In combination, a blade having a foot having axially extending sidesand transversely extending ends, a blade carrying member containing amating axially extending slot for receiving said blade foot, means forretaining said blade against movement in said slot comprising a pininserted through said blade carrying member to engage a recess locatedin said blade foot `and adjacent one of the ends of the foot of saidblade and the corresponding end of said slot, said recess extendingtransversely thereacross, said retaining pin having a shear strengthgreater than that of said blade foot, whereby a portion of said bladefoot may be readily broken oi to free said blade of said pin for removalof the blade.

3. In combination, a footed blade, a rotor member having a taperedsurface and containing a mating slot for cated near the end of saidblade toward which the blade is urged by said component ofcentrifugal'force, said pin being more resistantfto shear fracture thana portion of the blade foot on one side of said recess whereby the saidportion of said blade foot may be readily broken o to free said blade ofsaid pin for removal of the blade.

4. In combination, a blade having a frangible foothaving axiallyextending sides and transversely extending ends with an undercut portionthereon adjacent one end thereof, a blade carrying member having a slottherein receiving said blade foot and a relatively infrangible pininserted from said blade carrying member to engage the said undercutportion of said blade foot in said slot.

5. In combination, a footed blade having an undercut bottom portionforming a narrow lip with a part of the Y blade foot on one side of theundercut portion thereof,

receiving said blade foot, said blade having a component Y the thicknessof said lip measured in a generally axial direction of the blade beingseveral times less than that of the part of said blade foot on the otherside of said undercut portion, a blade carrying, member, having a slottherein for receiving said blade foot and a pin inserted from. saidblade carrying member to engage the said undercut portion of saidV bladefoot for retaining said blade, in said slot. e

6. In combination, a rotor blade havingranV enlarged foot thereon andcontaining an aperture' therein, a support member having a slot thereinforreceiving the foot of said blade, and a pin-like member carried bysaid support member and engaging the aperture in said blade foot toretain said blade in said slot, the aperture in said blade foot beingdisplaced from the center of the blade toward one end of the blade footand slot and the pin-like member being of higher resistance to shearfracture than the part of said bladerfoot between the aperture and theend of the blade foot adjacent said aperture, whereby the blade can bedestructibly released from said support member by sliding the bladelongitudinally of the slot thereby causing the pin to shear the saidpart of the blade foot.

References Cited in the ile of this patent UNITED STATES PATENTS 741,776Dodge Oct. 20, 1903 1,095,587 McIntosh May 5, 1914 1,535,417 Huff Apr.28, 1925 1,959,220 Robinson May l5, 1934 2,483,610 Baumann Oct. 4, 1949

